New Thermometer Reveals Wet Conditions on Earliest Earth

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New Thermometer Reveals Wet Conditions on Earliest Earth

Research paper to be published May 6 in
Science

Troy, N.Y. — Researchers at Rensselaer Polytechnic Institute
and Australian National University have found new evidence that
environmental conditions on early Earth, within 200 million
years of solar system formation, were characterized by
liquid-water oceans and continental crust similar to those of
the present day. The researchers developed a new thermometer
that made the discovery possible.

“Our data support recent theories that Earth began a pattern
of crust formation, erosion, and sediment recycling as early in
its evolution as 4.35 billion years ago, which contrasts with
the hot, violent environment envisioned for our young planet by
most researchers and opens up the possibility that life got a
very early foothold,” said E. Bruce Watson, Institute Professor
of Science and professor of geochemistry at Rensselaer
Polytechnic Institute.

According to Watson, the research provides important
information and a new technique for making additional
discoveries about the first eon of Earth’s history, the Hadean
eon, a time period for which still little is known.

The research findings are reported in the May 6 issue of the
journal Science in a paper titled “Zircon Thermometer
Reveals Minimum Melting Conditions on Earliest Earth.”

Watson collaborated with co-author T. Mark Harrison,
director of the Research School of Earth Sciences at Australian
National University and professor of geochemistry at UCLA, on
the research. The work was supported by the National Science
Foundation (NSF), the Australian Research Council, and the NASA
Astrobiology Institute.

Watson and Harrison developed a new thermometer that
involves the measurement of the titanium content of zircon
crystals to determine their crystallization temperature.
Zircons are tiny crystals embedded in rock that are the oldest
known materials on Earth. Zircons pre-date by 400 million years
the oldest known rocks on Earth. These ancient crystals provide
researchers with a window into the earliest history of the
Earth and have been used to date the assembly and movement of
continents and oceans.

“Zircons allow us to go further back in geologic time
because they survive processes that rocks do not,” said Watson.
“Although they measure only a fraction of a millimeter in size,
zircons hold a wealth of information about the very earliest
history of Earth.”

In Watson and Harrison’s work, zircons from the Jack Hills
area of Western Australia ranging in age from 4.0 to 4.35
billion years were analyzed using the thermometer. The new
temperature

data supports the existence of wet, minimum-melting
conditions within 200 million years of solar system formation,
according to the researchers. In the Science paper,
the researchers

discuss how the thermometer provides clear distinction
between zircons crystallized in the mantle, in granites, and
during metamorphism, thereby providing consistent information
about the conditions on Earth during the crystals’
formation.

Watson describes his research as “materials science of the
Earth,” because it involves designing and executing laboratory
experiments at the high temperatures and pressures found in the
Earth’s deep crust and upper mantle. He teaches
undergraduate and graduate geology courses at Rensselaer,
including Natural Sciences, Introduction to
Geochemistry, and Earth Materials.

Watson is a member of the National Academy of Sciences and a
fellow of the American Academy of Arts and Sciences, the
Geochemical Society, the American Geophysical Union, the
Mineralogical Society of America, the Geological Society of
America, and the European Association for Geochemistry. He has
been author or co-author for more than 150 peer-reviewed papers
on geochemistry, served on numerous academic editorial boards
and committees, and was recently recognized for his
contributions to the field with the 2005 V.M. Goldschmidt Medal
by the Geochemical Society. He received his Ph.D. in
geochemistry from Massachusetts Institute of Technology and
B.A. degree in geology from University of New Hampshire.

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About Rensselaer Polytechnic Institute

Founded in 1824, Rensselaer Polytechnic Institute is America’s first technological research university. Rensselaer encompasses five schools, 32 research centers, more than 145 academic programs, and a dynamic community made up of more than 7,900 students and more than 100,000 living alumni. Rensselaer faculty and alumni include more than 145 National Academy members, six members of the National Inventors Hall of Fame, six National Medal of Technology winners, five National Medal of Science winners, and a Nobel Prize winner in Physics. With nearly 200 years of experience advancing scientific and technological knowledge, Rensselaer remains focused on addressing global challenges with a spirit of ingenuity and collaboration.